The pH of a wound often signifies important information about wound health. Measuring the pH of a wound can provide information about the stage of healing and the presence of infection. The pH of wound leakage has been shown to change as the wound heals and if the wound becomes infected. The natural pH of skin is slightly acidic, ranging from 4.8 to 6.0, an adaptation which wards off bacteria on the surface, but the interstitial fluid in the body has a pH closer to neutral (Romanelli, M, et al., 2002). In healing wounds, pH starts slightly basic, moves to neutral, and then approaches the pH of normal skin (Gethin, G. 2007). Healthy wounds usually follow this trend, and it can be problematic if a wound does not. If healing is not progressing, the pH will stay basic. Wounds that remain basic usually heal more slowly because the tissue does not have enough access to oxygen. Small pH changes within a wound can cause large changes in oxygen availability (Leveen, H. et al., 1973). The more oxygen available in a wound, the faster a wound will heal. This makes pH fluctuations critical to wound health and the healing process.
Infection inhibits wound healing by raising wound pH. Many bacteria produce ammonia, which has a pH of 11.6 in a 1.0 M aqueous solution. Ammonia production raises the pH of a wound and lowers the oxygen availability. With a decreased oxygen supply, a wound will take much longer to heal (Leveen, H. et al., 1973). The bacteria present in an infection negatively affect the wound and its oxygen content. Bacteria and other factors can result in long periods of time in which the wound environment is at a basic pH. Because this can slow healing, measures are often taken to lower wound pH. Thus, measuring the pH of a wound can provide information about the stage of healing and the presence of infection.
Thus, there is a need for improved bandages capable of detecting pH to provide noninvasive, immediate information about a wound to help individualize treatment.